Woven ladder tape



-J. A. HENDLEY WOVEN LADDER TAPE Oct. 30, 1956 filed Jan. 22. 1954 v a my m W /Wbm m 2 Z Z my.

[Hz/en for James flffe'ndley fly Attorney United States Patent WOVEN LADDER TAPE James A. Hendley, Stanley, N. C., assignor to The Russell Manufacturing Company, Middletown, Conn, a corporation of Connecticut Application January 22, 1954, SerialNo. 405,643

i 1 Claim; (Cl. 139-384) This invention relates to improvements in woven ladder tape or webbing, also known as Venetian blind tape, and which is primarily employed for supporting the slats of Venetian blinds and the like, and which comprises a pair of front or face, and back or rear main tapes, between which extend the rungs or ladders which interconnect the two main tapes and which also support the slats of the blind.

One object of this invention is to provide an improved woven ladder tape which has a more beautiful appearance.

Another object of this invention is to provide an improved woven ladder tape which has greater resistance or imperviousness to absorption of dirt.

Other objects and advantages will appear to those skilled in the art from the following, considered in conjunction with the accompanying drawings.

In the description and claim, the various parts and steps are identified by specific terms for convenience, but they are intended to be as generic in their application as the prior art will permit.

In the accompanying drawings forming part of the present disclosure, in which certain ways of carrying out the invention are shown for illustrative purposes:

Fig. 1 is a side-edge view of a fragment of ladder tape made in accordance with the present invention, in completely closed or collapsed position;

Fig.2 is a view of the ladder tape of Fig. 1 in similar position, but in partly opened-out position;

Fig. 3 is a left-hand elevation of Fig. 2;

Fig. 4 is a view similar 'to Fig. 3, of an enlarged view of the area 4 thereof;

Fig. 5 is a schematic sectional view on line 5-5 of Fig. 4;

Fig. 6 is a sectional view on line 6-6 of Fig. 4;

Fig. 7 is a view similar to Fig. 4, of a different form of weave construction;

Fig. 8 is a schematic sectional view on line 8-3 of Fig. 7;

Fig. 9 is a sectional view on line 9-9 of Fig. 7;

Fig. 10 is a further-enlarged cross-sectional view of one of the plastic warp strands shown in Fig. 5;

Fig. 11 is an enlarged cross-sectional view of a modified form of plastic warp strand;

Fig. 12 is an enlarged cross-sectional view of another modified form of plastic warp strand; and

Fig. 13 is a schematic view showing in side elevation, one way of heat-treating the woven ladder tape.

Referring to Figs. 1 to 6 and 10 of the drawings showing the particular form of the invention chosen for illustration therein, the woven ladder tape includes the front or face main tape 21, and the back or rear main tape 22, with the two main tapes interconnected by ladders or rungs 23 which are connected to the main tapes preferably by weaving, in a way well understood by those skilled in the art.

Each of the main tapes 21 and 22 is formed by having warp strands 24 extending throughout the length of the 2. main tapes and interwoven with the weft picks of a weft strand 25. Each warp strand 24 is a monofilament plastic strand of considerably less maximum thickness than width, that is, of considerably greater width thanmaximum thickness.

The weft strand 25 is a continuous-multi-filament: strand of nylon which isformed of a plurality of continuous filaments 26, each filament being only a frac tion of one-thousandth of an inch in diameter. It; is ad-- vantageous to employ a continuous-multi-filarnent weft strand, whether it consists of a single strand or thread, or a plurality of threads plied or cabled together, having a twist of less than seven turns perinch in order to obtain a thinning and widening of'the'weft strand where it' presses .against the warp strands; somewhat similar to the. enlarged illustration in Figs. 4 to 9. Also, it will be seen from the schematic views of- Figs. 5 and 8, that the: thinned or flattened portions 25a of the weft strand 25, in conjunction with opposite side edge portions of theupper and lower oppositely-convex faces 24a and 24b of the warp strands 24, greatly aid the thinned or flattened portions 25a of the weft strand 25 in permitting the weftstrand to press the thin sharp edges 24c and 24d close: together to greatly aid in reducing the porosity, and consequently increasing the beauty, of the main tapes 21, 22.. A weft strand 25 made of nylon of two hundred and. ten' denier and having a twist of from one to three turns per inch is very satisfactory.

Nylon is quite elastic and when woven under tension, condenses the main tapes widthwise and thus reduces the; porosity of the main tapes, which tendency to porosity; normally tends to result from the normally relatively non-compressible monofilament plastic warp strands 24. Also the tendency to porosity is even further reduced or eliminated by'the heat treatment or heat setting which I give to the ladder tape, which softens the plastic warp, strands and also causes the nylon weft strand to shrink and pull the warp strands even closer together by cause ing the heat-softened sharp side edges of the warp strands to press or cut into one another. If desired, Qrlon, which has better resistance than nylon to ageing'in'sunlight, can; be employed as the weft strand instead of nylon, especially in the rear or back main tape which is exposed to. sunlight. Or anyother suitable continuous-multi-filament strand could be used for the weft strand.

Instead of employing the particular form of rnonofila ment plastic warp strand 24 illustrated in Fig. 10,: any other suitable shape of strand, such, for example, as the. strand 27 of Fig. 11, or strand 28 of Fig. 12 may be employed, although the strand 28 on account of its. blunt side edges, would not have some of the important advantages due to the sharp side edges of the forms of the strands 24 and 27. The width of the warp strand should be greater than its maximum thickness, preferably more. than twice as wide as its maximum thickness, even up to at least four times as wide. Thus a strand 24 of the shape and proportions shown in Fig. 10, which has been used by me of about five thousandths of an inch in maximum thickness, and of about twenty thousan'dths of an inch wide, gives very good results. For the purpose of having the main tapes sufiiciently bendable or flexible to fold properly in folds when the Venetian blind is raised, in a way well known to those skilled in the art, it is desirable that the maximum thickness of the monofilament warp strands shall be less than ten thousandths of an inch, and still more desirable, less than eight thousandths, and even more desirable, less than six thousandths of an inch.

Also it is highly advantageous that the shape of the warp strand shall be such that its upper and lower, or opposite faces, shall be oppositely convex, and that its opposite side edges shall be substantially sharp, or knifelike, or feather-edged, although this does not mean that the edges need to be knife-sharp. Thus in Fig. the strand 24 has the oppositely curved convex upper and lower faces 24a, 24b, and the substantially sharp opposite side edges 24c, 24d. I And the strand 27 of Fig-1'1 has the oppositely convex upper and lower faces 27a, 27b, and the substantially sharp opposite side edges 270, 27a, for reasons herein explained.

While the monofilament plastic warp strands may be made of any suitable plastic material, saran, which chemically is composed of copolymers of vinylidene chloride and vinyl chloride, gives very good results. Saran warp strands have a beautiful, smooth, non-absorbent glistening appearance, not only due to the saran material, but also due to the relatively large width and also the convexity, of the individual warp strands.

By suitably heat treating ladder tape woven of saran warp strands as hereinafter explained, they are rendered even more easily bendable. After the ladder tape is woven as hereinbefore explained, it is advantageous to heat-treat it as now to be described, and as schematically illustrated in Fig. 13. For this purpose, a quantity of woven ladder tape in collapsed position with its main tapes 21 and 22 close together as shown in edge view in Fig. 1, is wound upon a reel 29 which is rotatably supported near the first pair of annular feed rolls 30, 31, and is passed by hand through the feed rolls 30, 31, with one side edge of the tape being toward the eye of a person looking toward the construction shown in Fig. 1, and with one upper infra-red heating element 32 spaced about eight and one-half inches above the longitudinal middle of the upper face of the tape 20, and with another lower infra-red heating element 33, spaced about eight and one-half inches below the longitudinal middle of the lower face of the tape 20. The tape 20 is then passed between the second pair of feed rolls 34, 35, and then through the openings 36, 37, in the cooling chamber 38, and then through the third pair of feed rolls 39, 40, and down below the top of the open-top receiving receptacle 41. An air-entrance opening 42, in the bottom wall 43, of the cooling chamber 38, directly below the tape 20, is to permit air of ordinary room temperature to be blown into the cooling chamber by a blower (not shown).

Preferably, the three upper feed rolls 30, 34, and 39, are of relatively soft material such as soft vulcanized rubber, or other elastomer material such as Hy-Car, for example, and the'three lower feed rolls 31, 35, and 40 can be of steel or other suitable materials.

In an embodiment similar to Fig. 13, that has been successfully used, all the feed rolls are each of about three inches diameter. Each heater-unit, or element, 32, 33, is a Weigand Chromalox unit, and the units 32 and 33 are electrically heated by current sent through their respective terminal wires 32a and 33a in the usual way. The upper unit 32 is preferably of fifteen hundred watts, and the lower uni-t 33 is of eighteen hundred watts, and each unit 32, 33 is about thirty nine inches long. The cooling chamber 38 is about forty five inches long.

In operation, the second pair of feed rolls 34, are driven at the same and constant speed by a motor (not shown). The third pair of feed rolls 39, 40 are driven with, and at the same speed as, the feed rolls 34, 35. The first pair of feed rolls 30, 31 are driven at a somewhat higher speed than the other feed rolls for a reason that will be presently explained.

The ladder tape 20 is fed past in between the heating elements or units 32, 33 at about sixteen feet per minute. This exposure of each part of the surface of both sides or faces of the tape 20 for the several seconds of time involved, results in heating and temporarily softening, and permanently increasing the bendability of, the plastic warp strands 24. And the heat also permanently shortens the strands 24, and consequently the tape 20, a distance of several inches per yard of original length to thus reduce the tendency of the tape 20 to later shrink with ageing. It is because of this longitudinal shrinking action of the ladder tape 20, that the first pair of feed rolls are driven at a higher speed than the second and third pairs of feed rolls, in order to permit controlled longitudinal shrinking of the ladder tape 20. If so desired, the speed of the feed rolls 30, 31 can be increased, or decreased, by hand control or otherwise. In order to maintain the temperature to which the tape is heated, fairly constant, one way this can be done is to employ a Cramer input controller (not shown) which can be adjusted and set to give any desired preselected on and off time-periods of seconds for the heating current to the heating units 32 and 33.

Another way of heat treating, or heat setting the ladder tape, is to submerge it in, or pass it through, boiling-hot water to accomplish the results previously described as accomplished by the radiant-heat method.

The exposure of the tape 20 to the heat, also at the same time causes the picks of the weft strand to shrink and press the adjacent sharp side edges of the warp strands 24 against one another and cause them to cut into each other a substantial distance, to thus further densify and reduce the porosity of the main tapes 21, 22 of the ladder tape 20.

The invention may be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all the changes coming within the meaning and equivalency range of the appended claim are intended to be embraced therein.

I claim:

A ladder tape comprising two main tapes, and ladders interconnecting the main tapes, at least one of the main tapes being formed of a continuous multifilament transverse weft strand having less than seven turns per inch of twist, and longitudinal plastic warp strands woven together, each said plastic warp strand being a monofilament plastic strand of considerably less maximum thickness than width, and having its two wider faces oppositely convex and disposed in the opposite surfaces of said main tape whereby the transverse folding of the main tape is facilitated.

References Cited in the file of this patent UNITED STATES PATENTS 2,354,435 Stedman July 25, 1944 2,551,175 Smith May 1, 1951 2,613,694 French et a1 Oct. 14, 1952 

